It is frequently found necessary to connect the output voltage amplifier to a capacitive load. For example, where a load is physically located an appreciable distance from the driving amplifier, a co-axial cable is typically used to connect the load to the amplifier. This cable will look like a shunt capacitor to the output stages of the amplifier. Another example is where an amplifier is to be connected to a piezo-electric transducer, or the like, which also looks like a shunt capacitor to the driving source.
When, in addition to the above, the amplifier is called upon to deliver a high-voltage, low-distortion output signal, the known circuit designs fail because the prior art high-voltage amplifiers invariably have a high output impedance and are, hence, unsuitable for use with capacitive loads.